The invention is concerned with a process for preparing 2,2-bis (3,5-di-t-butyl-4-hydroxyphenyl)propane by reacting isobutylene with diphenylolpropane and with 2,2-bis(3,5-di-t-butyl-4-hydroxyphenyl)propane so formed.
It is known from U.K. Pat. specification No. 781,768 to alkylate bisphenylol alkanes in the presence of solvents and Friedel-Craft catalysts such as sulfuric acid, p-toluene sulfonic acid, boron trifluoride and acid-activated clays. As can be seen from the examples of the said U.K. specification this process results in a poor yield of the desired tetraalkylated bisphenylol alkane which is also difficult to isolate. The reason for this is that, unlike the alkylation of monophenols e.g. phenol itself, a competitive reaction accompanies the alkylation of bisphenol alkanes. This competitive reaction is the cleavage of the bisphenolic skeleton to form phenol and alkyl phenol followed by the disproportionation, polymerization and alkylation thereof. This competitive reaction is particularly a problem when it is desired to produce mainly the tetra-alkylated derivatives.
It has now been discovered that, by carrying out the reaction between isobutylene and diphenylolpropane in the presence of a substantially anhydrous aromatic sulfonic acid a reaction product containing improved yields of desired tetra-alkylated product is obtained from which the desired product may easily be extracted.
2,2-BIS(3,5-DI-T-BUTYL-4-HYDROXYPHENYL)PROPANE IS USED FOR A VARIETY OF PURPOSES SUCH AS FOR THE STABILIZATION OF NATURAL OR SYNTHETIC RUBBERS AND PLASTICS.